Title

Author

Date of Award

1-2004

Document Type

Thesis

Degree Name

Master of Science in Material Science Engineering (MSMatSE)

Department

Materials Science

First Advisor

Dr. Adel Hammami

Second Advisor

Dr. Abdullah Al-Khanbashi

Abstract

The use of biomaterials in orthopedic surgery has been successfully acceptable in the current medical practice. Total hip joint replacement (THR) is one of the most popular and successful operations in orthopedics. Total hip replacement (THR) has been using metal prosthesis for many years. However, the use of metal implants has two major disadvantages. The first disadvantage is that the stiffness of the metallic prosthesis is relatively high compared to the surrounding, load carrying bone. The elastic moduli of titanium and cobalt-chromium alloy are 110 and 210 GPa, respectively. Whereas the elastic modulus of cortical bone ranges from 15 to 25 GPa. This mismatch between the bone and the stiffness of the implant will cause the degradation of the bone-implant interface, which will lead eventually to loosening and prosthesis fracture. The second disadvantage of metallic prosthesis is the release of harmful metal ions, which may cause hypersensitivity to the patient.

To overcome the stiffness problem and other related metal implants complications, recent advances in design and manufacturing technologies proposed the use of composite materials as an alternative to the metallic implants. The use of composite materials in orthopedic surgery offers a variety of new implant designs. Outstanding mechanical properties; radiolucency, biocompatibility and low weight are the major advantages compared with metals in clinical use today. Composite materials are known as low stiffness materials with mechanical properties close to the properties of bone. The strength and stiffness of composite materials can be varied easily when compared to metals. For example, the strength varies from 70 MPa to 1900 MPa and stiffness varies from 1.0 GPa to 170 GPa. Such tailorability in strength and stiffness could provide a state of stress in the femur closer to physiological level. Thus, it will eliminate the problems of bone-prosthesis loosening and prosthesis fracture.

The main goal of this thesis is to investigate the performance of woven composites for a hip prosthesis made from hybrid materials. For such a purpose, field investigation was conducted locally to establish a realistic ground for the total hip replacement procedures in the U.A.E. This field investigation revealed that the THR cases performed in the U.A.E. are exponentially increasing every year. This increase in the THR cases requires an immediate solution for the problem.

For the purpose of this design, two types of fibers were used to manufacture the specimens. The first type of fiber is the E-glass fiber. The second type of the fiber is the hybrid carbon-aramid fiber reinforced vinyl ester resin. Two types of processing techniques were used to manufacture specimens. The techniques were hot press molding and vacuum infusion. The specimens were then divided into three groups and each group contains eight specimens. Some specimens were kept immersed in a physiological solution for eight weeks, while others were used as virgin specimens.

The evaluation process included mechanical test, weight gain calculation for the glass fiber and the scanning-electron microscopy (SEM) study. In this study, we found that immersion in the physiological solution caused reduction in strength and modulus of the composite materials manufactured by vacuum infusion technique. On the other hand, weight reduction did not occur for the glass fiber manufactured by hot press molding. This is due to the lack of adequate resin available in the fiber-matrix interface. Scanning-electron microscopy (SEM) study examined and showed the fractures' surfaces occurred to the specimen.

Fatigue tests performed on conditioned specimens have shown that the main failure mechanism can be attributed to the poor interface between the fiber and the matrix.